Method for preparing super-high purity rare earth chelate

Abstract

This invention discloses an ultra-high purity rare earth chelate and its preparation method. A mixed solution is formed by combining a rare earth element salt, a β-dicarbonyl compound, a crystallization regulator, and a solvent. The pH of the mixed solution is adjusted to 7.5-8.0 by regulating the amount of crystallization regulator. Solid-liquid separation is performed to obtain a crude rare earth chelate. The crude rare earth chelate is then purified by sublimation to obtain an ultra-high purity rare earth chelate. This invention achieves kilogram-scale production of ultra-high purity Er(TMHD)3. It has significant industrialization potential, with a product yield ≥95%, stable purity, and no scale-up effect.

Description

Technical Field

[0001] This invention relates to the field of organic compound preparation technology, and in particular to a method for preparing ultra-high purity rare earth chelates. Background Technology

[0002] Ultra-high purity rare-earth chelates serve as key doping sources in optical fiber preform manufacturing, providing gain ions for optical amplifiers. Improving fiber performance hinges on increasing the purity of rare-earth chelates. Alkali metal impurities can form charge traps, while transition metal impurities can generate strong absorption peaks in communication bands, leading to signal attenuation or distortion. However, traditional methods for preparing rare-earth chelate crystals use strong bases such as NaOH, KOH, or triethylamine, which not only introduce alkali metal impurities but also cause localized over-alkali formation during preparation, generating hydroxide colloids. The hydroxyl groups in these colloids can interfere with signal transmission. Therefore, preparing ultra-high purity rare-earth chelates has become a crucial material for developing high-power optical fiber preforms. Summary of the Invention

[0003] Therefore, it is necessary to provide an ultra-high purity rare earth chelate and its preparation method, which can prepare ultra-high purity rare earth chelates without introducing other metal impurities and without causing local over-alkaliness.

[0004] One aspect of this application provides a method for preparing ultra-high purity rare earth chelates, comprising the following steps: forming a mixed solution of a rare earth element salt, a β-dicarbonyl compound, a crystallization regulator, and a solvent and reacting the mixture; separating the solid and liquid phases of the reaction solution to obtain a crude rare earth chelate; wherein the pH of the mixed solution is adjusted to 7.5-8.0 by adjusting the amount of the crystallization regulator, wherein the crystallization regulator includes a polycyclic amine compound; and the crude rare earth chelate is then purified by sublimation to obtain an ultra-high purity rare earth chelate.

[0005] The method for preparing the aforementioned ultra-high purity rare earth chelates in this application uses polycyclic amine compounds as crystallization regulators, which can replace strong alkalis. These polycyclic amine compounds do not contain Na. + K + The presence of alkali metal ions prevents the introduction of alkali metal impurities at the source. Simultaneously, due to their polycyclic structure, the polycyclic amine compounds release NH3 slowly during hydrolysis, resulting in chelation in the mixed reaction. The pH of the system rises slowly during the reaction, maintaining a relatively mild reaction environment and preventing the adverse effects of localized over-alkaliness on purity. The crude chelate is then purified by sublimation to obtain ultra-high purity rare earth chelates, thereby reducing the alkali metal impurity content and improving the purity of the rare earth chelates.

[0006] In some embodiments, the polycyclic amine compound has a cage-like polycyclic structure.

[0007] In some embodiments, the crystallization regulator is selected from at least one of hexamethylenetetramine, triethylenediamine, quinine ring, and adamantane.

[0008] Optionally, the crystallization regulator is hexamethylenetetramine.

[0009] In some embodiments, the temperature of the mixed solution is 0 °C–40 °C; and / or,

[0010] The process of forming a mixed solution from rare earth element salts, β-dicarbonyl compounds, crystallization regulators, and solvents includes the following steps:

[0011] A rare earth element salt solution and a β-dicarbonyl compound solution are mixed to form an intermediate solution; a solution of the crystallization regulator is gradually added to the intermediate solution.

[0012] Optionally, the concentration of the crystallization regulator solution is 0.1 mol / L to 0.3 mol / L.

[0013] In some embodiments, the concentration of the rare earth element salt solution is 0.1 mol / L-0.4 mol / L, the concentration of the β-dicarbonyl compound solution is 0.4 mol / L-1.2 mol / L, and the volume ratio of the rare earth element salt solution to the β-dicarbonyl compound solution is 1:1-1:2.

[0014] In some embodiments, the rare earth element salt is selected from at least one of cerium salts, ytterbium salts, and erbium salts; and / or, the β-dicarbonyl compound is selected from at least one of 2,2,6,6-tetramethyl-3,5-heptadecylone, acetylacetone, and dibenzoylmethane.

[0015] In some embodiments, after the solid-liquid separation and before obtaining the crude rare earth chelate, the following step is further included: washing the crude rare earth chelate with water until the conductivity of the water wash filtrate is <5 µS / cm.

[0016] In some embodiments, the crude rare earth chelate is purified by sublimation, including the following steps.

[0017] The crude rare earth chelate was purified by sublimation using a vacuum sublimation furnace. The vacuum sublimation furnace was divided into a sublimation zone, a condensation deposition zone, and a cold trap zone according to its spatial location and operating temperature.

[0018] Furthermore, the operating temperature of the sublimation zone is greater than or equal to the operating temperature of the condensation deposition zone, and the operating temperature of the condensation deposition zone is greater than the operating temperature of the cold trap zone.

[0019] In some embodiments, the operating temperature of the sublimation zone is 190 ℃-210 ℃, and the operating temperature of the condensation deposition zone is 150 ℃-170 ℃.

[0020] In some embodiments, the multi-stage heating and holding process of the sublimation zone includes the following steps: first heating to 130 ℃-150 ℃ and holding for 1 h-3 h, then heating to 190 ℃-210 ℃ and holding for 2 h-4 h;

[0021] The multi-stage heating and heat preservation process of the condensation deposition zone includes the following steps: first, heating to 130 ℃-150 ℃ and holding for 1 h-3 h, then heating to 150 ℃-170 ℃ and holding for 2 h-4 h. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the principle and process of preparing ultra-high purity rare earth chelates in this application;

[0023] Figure 2 This is a schematic diagram of the temperature zones of the multi-temperature zone vacuum sublimation furnace in this application;

[0024] Figure 3 This is a photograph of the ultra-high purity rare earth chelate crystals obtained in Example 1 of this application;

[0025] Figure 4 The X-ray diffraction pattern of the ultra-high purity rare earth chelate obtained in Example 1 of this application;

[0026] Figure 5 Thermogravimetric-differential thermal curve of the ultra-high purity rare earth chelate prepared in Example 1 of this application. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] In traditional methods using strong alkali metal bases, strong base chelation can lead to localized over-alkaliness and significant exothermic reactions. This results in the violent release and rapid diffusion of OH-.- This can cause localized pH spikes in the solution, irreversibly forming hydroxide colloids and affecting the purity of the product. Therefore, to reduce the impact of localized over-alkaliness and excessive exothermic reactions on purity, the chelation environment is artificially controlled to be low temperature and inert atmosphere. However, this increases the process requirements and energy consumption for preparing ultra-high purity rare earth chelates, raising the barrier to entry. Regarding pollutant treatment, alkali metal ions are difficult to degrade and remove using conventional precipitation processes. Scaling up traditional processes to large-scale production results in pollution, which is a major challenge for the industrial production of ultra-high purity rare earth chelates.

[0030] The following is a comparison of the Chinese and English versions or abbreviations in this application:

[0031] TMHD-2,2,6,6-Tetramethyl-3,5-heptadecylene, HMTA-Hexamethylenetetramine, 3N5-99.5%, 4N-99.99%, 5N-99.999%, 6N-99.9999%, ICP-MS-Inductively Coupled Plasma Mass Spectrometry, XRD-X-ray Diffraction, TG-Thermogravimetric Analysis, DTA-Differential Thermal Analysis, ICDD-International Data Center for Diffraction.

[0032] A method for preparing ultra-high purity rare earth chelates includes the following steps S10-S20:

[0033] S10. A mixed solution is formed by combining rare earth element salt, β-dicarbonyl compound, crystallization regulator and solvent and reacted. The reaction solution is then separated into solid and liquid phases to obtain crude rare earth chelate. The pH of the mixed solution is adjusted to 7.5-8.0 by adjusting the amount of crystallization regulator. The crystallization regulator includes polycyclic amine compounds.

[0034] S20. The crude rare earth chelate is sublimated and purified to obtain ultra-high purity rare earth chelate.

[0035] The method for preparing the aforementioned ultra-high purity rare earth chelates in this application uses polycyclic amine compounds as crystallization regulators, which can replace strong alkalis. These polycyclic amine compounds do not contain Na. + K + The presence of alkali metal ions prevents the introduction of alkali metal impurities at the source. Simultaneously, due to their polycyclic structure, the polycyclic amine compounds release NH3 slowly during hydrolysis, resulting in chelation in the mixed reaction. The pH of the system rises slowly during the reaction, maintaining a relatively mild reaction environment and preventing the adverse effects of localized over-alkaliness on purity. The crude chelate is then purified by sublimation to obtain ultra-high purity rare earth chelates, thereby reducing the alkali metal impurity content and improving the purity of the rare earth chelates.

[0036] Furthermore, the crystallization regulator is a polycyclic amine compound, and no strong base is added.

[0037] In some embodiments, the polycyclic amine compounds have a cage-like polycyclic structure. The hydrolysis of polycyclic amine compounds with a cage-like polycyclic structure is more controllable, allowing for the slow release of NH3 during chelation, resulting in a gradual increase in the pH of the system, which is beneficial for further improving the purity of the rare earth chelates.

[0038] In some embodiments, the crystallization regulator includes at least one of hexamethylenetetramine, triethylenediamine, quinine ring, and adamantane. These crystallization regulators all have cage-like polycyclic structures, which can slowly release NH3, thus helping to further improve the purity of the rare earth chelate.

[0039] In some embodiments, the crystallization regulator is hexamethylenetetramine.

[0040] Optionally, the purity of hexamethylenetetramine is ≥4N.

[0041] This application utilizes crystallization regulators such as hexamethylenetetramine, resulting in wastewater containing trace amounts of hexamethylenetetramine and ammonia nitrogen, which meets the standards for direct discharge through biochemical treatment, aligning with the concept of green chemistry.

[0042] Taking hexamethylenetetramine as an example, the principle and process of adjusting the pH of a solution using HMTA are as follows: Figure 1 As shown, HMTA hydrolyzes, slowly releasing NH3. The released NH3 reacts with water to form OH-. - The generated OH - The chelate diffuses at a uniform rate in the solution, preventing local pH from becoming too high, and the chelate will nucleate and precipitate uniformly.

[0043] In some of these embodiments, the concentration of the crystallization regulator is 0.1 mol / L to 0.3 mol / L.

[0044] In some embodiments, a mixed solution is formed by combining a rare earth element salt, a β-dicarbonyl compound, a crystallization regulator, and a solvent, including the following steps: mixing a rare earth element salt solution and a β-dicarbonyl compound solution to form an intermediate solution; and gradually adding a crystallization regulator to the intermediate solution.

[0045] Furthermore, the concentration of the crystallization regulator solution is 0.1 mol / L to 0.3 mol / L. As an example, the concentration of the crystallization regulator solution can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, or any two of the above values ​​within the range.

[0046] Furthermore, the crystallization regulator is added at a rate of 50 mL / min to 100 mL / min. As an example, the concentration of the crystallization regulator solution can be 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, or any two of the above values.

[0047] Alternatively, the crystallization regulator solution can be added gradually by dropping.

[0048] Optionally, the intermediate solution can be gradually added to while the intermediate solution is stirred.

[0049] Furthermore, the stirring speed is 400 rpm-500 rpm.

[0050] Furthermore, the solvent for the crystallization regulator solution can be water.

[0051] Furthermore, the solvent for rare earth element salt solutions can be water.

[0052] Furthermore, the solvent for the β-dicarbonyl compound solution can be ethanol.

[0053] In some embodiments, the mixing reaction is carried out at a temperature of 0-40 °C. Alternatively, it is carried out at 25 ± 5 °C.

[0054] The preparation method of the above-mentioned ultra-high purity rare earth chelates in this application reduces the requirements of the preparation process of ultra-high purity rare earth chelates because the hydrolysis process of polycyclic amine compounds is relatively slow.

[0055] In some of these embodiments, the mixing reaction time can be 3 h to 6 h.

[0056] In some embodiments, the temperature of the Xingcheng mixed solution in step S10 is 0-40 °C. Optionally, it is 25±5 °C.

[0057] In some embodiments, the concentration of the rare earth element salt solution is 0.1 mol / L-0.4 mol / L, the concentration of the β-dicarbonyl compound solution is 0.4 mol / L-1.2 mol / L, and the volume ratio of the rare earth element salt solution to the β-dicarbonyl compound solution is 1:1-1:2.

[0058] In some embodiments, the rare earth element salt is selected from at least one of cerium salt, ytterbium salt, and erbium salt, and the β-dicarbonyl compound is selected from at least one of 2,2,6,6-tetramethyl-3,5-heptadecane, acetylacetone, and dibenzoylmethane.

[0059] Optionally, the rare earth element salt is an erbium salt, and the β-dicarbonyl compound is 2,2,6,6-tetramethyl-3,5-heptadecane.

[0060] Furthermore, the concentration of the erbium salt solution was 0.17 mol / L-0.34 mol / L, and the concentration of the 2,2,6,6-tetramethyl-3,5-heptadecane solution was 0.51 mol / L-1.02 mol / L.

[0061] Furthermore, the erbium salt solution is prepared by ErCl3·6H2O crystals and ultrapure water, wherein the purity of ErCl3·6H2O crystals is ≥6N, the purity of 2,2,6,6-tetramethyl-3,5-heptadecane is ≥6N, and the conductivity of ultrapure water is ≥18 MΩ cm.

[0062] In some embodiments, after solid-liquid separation and before obtaining the crude rare earth chelate, the following step is further included: washing the solid material obtained after solid-liquid separation with water until the conductivity of the water wash filtrate is <5 µS / cm.

[0063] In some embodiments, the crude rare earth chelate is purified by sublimation, including the following steps.

[0064] The crude rare earth chelate was purified by sublimation using a vacuum sublimation furnace. The areas in the vacuum sublimation furnace were divided into a sublimation zone, a condensation deposition zone, and a cold trap zone according to their spatial location and operating temperature.

[0065] Furthermore, the operating temperature of the sublimation zone is greater than or equal to the operating temperature of the condensation deposition zone, and the operating temperature of the condensation deposition zone is greater than the operating temperature of the cold trap zone.

[0066] Furthermore, the middle section of the vacuum sublimation furnace is the sublimation zone, the two ends of the vacuum sublimation furnace are cold trap zones, and the area between the cold trap zone and the sublimation zone is the condensation deposition zone; for example... Figure 2 As shown.

[0067] In some embodiments, the operating temperature of the sublimation zone is 190 ℃-210 ℃. For example, the operating temperature of the sublimation zone is within the range of 190 ℃, 200 ℃, 210 ℃, or any two of the above values. The operating temperature of the condensation deposition zone is 150 ℃-170 ℃. For example, the operating temperature of the condensation deposition zone is within the range of 150 ℃, 160 ℃, 170 ℃, or any two of the above values.

[0068] In some embodiments, the multi-stage heating and holding process of the sublimation zone includes first heating to 130 ℃-150 ℃ and holding for 1 h-3 h, and then heating to 190 ℃-210 ℃ and holding for 2 h-4 h.

[0069] The multi-stage heating and holding process in the condensation deposition zone includes first heating to 130 ℃-150 ℃ and holding for 1 h-3 h, then heating to 150 ℃-170 ℃ and holding for 2 h-4 h.

[0070] Optionally, the multi-stage heating and holding process of the sublimation zone includes first heating to 140 ℃ and holding for 12 h to remove residual moisture and pre-remove low-boiling-point impurities, and then heating to 200 ℃ and holding for 3 h.

[0071] The multi-stage heating and holding process of the condensation deposition zone includes first heating to 140 ℃ and holding for 2 h, then heating to 160 ℃ and holding for 3 h;

[0072] The cold trap area does not undergo a heating and insulation process; the temperature is maintained at 0-40 ℃, or optionally 25±5 ℃, to capture volatile impurities.

[0073] The method for preparing ultra-high purity rare earth chelates described in this application utilizes different temperature zones in a vacuum sublimation furnace to achieve spatial separation of rare earth chelates and impurities. The sublimation zone is used to control the sublimation of crude rare earth chelates, the condensation deposition zone is used to selectively trap rare earth chelate vapors to form ultra-high purity rare earth chelate crystals, and the cold trap zone is used to capture volatile impurities. This achieves the function of spatial separation and directional purification. By utilizing the vapor pressure difference between different substances and the temperature gradient between multiple temperature zones, the physical separation of rare earth chelate crystals and impurities is achieved, improving the traditional single-temperature zone overall heating process and achieving the purpose of precision fractionation.

[0074] The following are specific examples.

[0075] Example 1

[0076] Step 1: Prepare 5 L of 0.34 mol / L ErCl3 solution, 5 L of 1.02 mol / L TMHD solution, and 0.3 mol / L HMTA solution. The solvents for ErCl3 and HMTA solutions are ultrapure water, and the solvent for TMHD solution is anhydrous ethanol. Use ErCl3·6H2O crystals with a purity of 6N to prepare the ErCl3 solution. The purity of TMHD must be ≥6N, and the purity of HMTA must be ≥4N.

[0077] Step 2: Mix ErCl3 solution and TMHD solution in a 1:1 volume ratio in the reactor. Start the stirrer at 500 rpm, maintaining the solution temperature in the reactor at 25±5 ℃. Slowly inject HMTA solution into the reactor at a rate of 50 mL / min. Monitor the pH value in real time using a pH meter, and stop injecting HMTA solution when the pH reaches 7.8. Maintain stirring for 4 h until a large amount of rose-red Er(TMHD)3 precipitate appears. Add 20 L of ultrapure water to the reactor, continue stirring for 1 h to dilute residual ethanol and promote the aggregation of Er(TMHD)3 precipitate particles, then stop stirring and let stand for 30 min.

[0078] Step 3: Transfer the liquid from the reactor into a vacuum filtration device for vacuum filtration using a polytetrafluoroethylene microporous membrane with a pore size of approximately 0.45 µm. Rinse the filtrate four times with 10 L of ultrapure water and measure the conductivity of the filtrate, controlling it to be <5 µS / cm to reduce Cl content in the solids. - The solid obtained by filtration was dried in a vacuum drying oven at 65 °C and -0.1 MPa for 8 h to remove moisture, and crude Er(TMHD)3 was obtained with a moisture content of <0.1 wt%.

[0079] Step 4: Spread the crude product in a crucible to a thickness of ≤1 cm. Place the crucible in a multi-temperature zone vacuum sublimation furnace with a vacuum degree of approximately 0.01 Pa for purification. Place the crucible in the sublimation zone. Refer to the attached diagram for the positions of each temperature zone in the vacuum sublimation furnace. Figure 3 The sublimation and condensation deposition zones are controlled by a multi-stage heating and holding program to fractionate and purify Er(TMHD)3 and its impurities. The sublimation and condensation deposition zones are controlled by a segmented holding program, specifically as follows:

[0080] The sublimation zone was first heated to 140 ℃ at a rate of 5 ℃ / min and held for 2 h, then heated to 200 ℃ at a rate of 5 ℃ / min and held for 3 h; the condensation deposition zone was first heated to 140 ℃ at a rate of 5 ℃ / min and held for 2 h, then heated to 160 ℃ at a rate of 5 ℃ / min and held for 3 h.

[0081] The cold trap area does not undergo a heating process, and the temperature is maintained at 25±5 ℃.

[0082] After the heat preservation is completed and the material is cooled, the Er(TMHD)3 crystals deposited in the condensation deposition zone are collected under an inert atmosphere and placed into an aluminum-plastic composite vacuum bag, which is then filled with nitrogen and heat-sealed.

[0083] Example 2

[0084] The preparation method of Example 2 is basically the same as that of Example 1, except that 0.1 mol / L HMTA solution is used instead of 0.3 mol / L HMTA solution in Example 1.

[0085] Example 3

[0086] The preparation method of Example 3 is basically the same as that of Example 1, except that: 10 L of 0.17 mol / L ErCl3 solution is used to replace 5 L of 0.34 mol / L ErCl3 solution, and 10 L of 0.51 mol / L TMHD solution is used to replace 5 L of 1.02 mol / L TMHD solution. That is, the concentrations of ErCl3 solution and TMHD solution are reduced to half of those in Example 1, and the volume of solution is increased to twice that of Example 1.

[0087] Example 4

[0088] The preparation method of Example 4 is basically the same as that of Example 1, except that the working temperature of the sublimation zone is reduced from 200 °C to 190 °C.

[0089] Comparative Example 1

[0090] The preparation method used in Comparative Example 1 is basically the same as that used in Example 1, except that a strong alkaline solution with a concentration of 0.3 mol / L NaOH is used instead of the 0.3 mol / L HMTA solution in Example 1, and the injection of the strong alkaline solution is stopped when the pH reaches 7.8.

[0091] The Er(TMHD)3 obtained in each example was tested. Purity was determined by the difference method (100% - percentage content of impurities). Er content was determined by ethylenediaminetetraacetic acid titration. Product yield was calculated by mass yield using the method of actual amount of Er(TMHD)3 produced / theoretical amount of Er(TMHD)3 produced × 100%. The content of each impurity element was determined by ICP-MS.

[0092] A photograph of the ultra-high purity rare earth chelate crystals obtained in Example 1 of this application, as shown. Figure 3 As shown;

[0093] XRD analysis of the ultra-high purity rare earth chelate prepared in Example 1 of this application showed that... Figure 4 As shown; the obtained ultra-high purity erbium chelate crystal corresponds to No. Er(C 11 H 19 O2)3 00-048 card, high purity, no impurity peaks and good crystallization properties.

[0094] The TG-DTA curve of the ultra-high purity rare earth chelate obtained in Example 1 of this application is shown below. Figure 5 As shown.

[0095] Some parameters and results are shown in Table 1.

[0096] Table 1

[0097]

[0098] Comparative studies of Examples 1-3 show that the Er(TMHD)3 crystals obtained in this application, through a combination of gentle chelation and spatial separation for impurity removal, have a purity ≥6N, H2O residue <100 ppm, alkali metal impurities <0.5 ppm, and other impurity elements reach the ppb level. Furthermore, the weight of ultra-high purity Er(TMHD)3 crystals obtained in a single batch can reach the kilogram level, approximately 1 kg-2.5 kg, with a product yield ≥95%.

[0099] A comparison of Examples 2 and 1 shows that the method for preparing ultra-high purity rare earth chelates disclosed in this application utilizes polycyclic amine compounds to replace strong bases, thereby controlling the factors that cause pH runaway from the source. Specifically, the slow release of NH3 through HMTA hydrolysis provides a wider concentration operating window, and the chelation reaction system can withstand fluctuations in HMTA dosage, reducing the difficulty of industrial-scale operation and demonstrating that ultra-high purity Er(TMHD)3 crystals can still be prepared at low concentrations.

[0100] By comparing Example 3 and Example 1, it can be seen that the method for preparing ultra-high purity rare earth chelates disclosed in this application, under the premise of keeping the total molar amount of reactants constant, doubles the volume, simulating the mass transfer efficiency and reaction uniformity in a large-volume reactor. The method disclosed in this application has the potential to be linearly scaled up to the industrial 100 L level production.

[0101] By comparing Example 4 and Example 1, it can be seen that in the method for preparing ultra-high purity rare earth chelates disclosed in this application, the yield of Er(TMHD)3 crystal product decreases to 85.31% when the second temperature of the sublimation zone is reduced to 190 °C. Therefore, the working temperature of the sublimation zone needs to be controlled at 200±5 °C to further improve the product yield.

[0102] By comparing Comparative Example 1 with Examples 1-4, it can be seen that the purity of the Er(TMHD)3 crystals prepared in Comparative Example 1 is 3N5, proving that the traditional strong base system is not applicable to the preparation method of ultra-high purity rare earth chelates disclosed in this application. Therefore, it is proven that in this application, the use of HMTA to replace NaOH strong base avoids the introduction of alkali metal element impurities and the adverse effects of local over-alkali on purity from the source.

[0103] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an ultra-high purity rare earth chelate, characterized by, Includes the following steps S10-S20: S10. A mixed solution is formed by combining rare earth element salts, β-dicarbonyl compounds, crystallization regulators, and solvents, and the mixture is reacted. The reaction solution is then separated into solid and liquid phases to obtain a crude rare earth chelate. The pH of the mixed solution is adjusted to 7.5-8.0 by adjusting the amount of the crystallization regulator, which includes polycyclic amine compounds. S20. The crude rare earth chelate is sublimated and purified to obtain ultra-high purity rare earth chelate. The polycyclic amine compound is selected from at least one of hexamethylenetetramine, triethylenediamine, and quinine ring; The rare earth element salt is selected from at least one of cerium salt, ytterbium salt, and erbium salt; The β-dicarbonyl compound is selected from at least one of 2,2,6,6-tetramethyl-3,5-heptanedione, acetylacetone, and dibenzoylmethane; After the solid-liquid separation and before obtaining the crude rare earth chelate, the following steps are also included: washing the crude rare earth chelate with water until the conductivity of the water washing filtrate is <5 µS / cm. The crude rare earth chelate was purified by sublimation, including the following steps: The crude rare earth chelate was purified by sublimation using a vacuum sublimation furnace. The areas in the vacuum sublimation furnace were divided into a sublimation zone, a condensation deposition zone, and a cold trap zone according to their spatial location and operating temperature. Furthermore, the operating temperature of the sublimation zone is greater than or equal to the operating temperature of the condensation deposition zone, the operating temperature of the condensation deposition zone is greater than the operating temperature of the cold trap zone, and the operating temperature of the condensation deposition zone is 150 ℃-170 ℃.

2. The method for preparing the ultra-high purity rare earth chelate as described in claim 1, characterized in that, The polycyclic amine compounds have a cage-like polycyclic structure.

3. The method for preparing the ultra-high purity rare earth chelate as described in claim 1, characterized in that, The temperature of the mixed solution is 0 ℃-40 ℃.

4. The method for preparing the ultra-high purity rare earth chelate as described in claim 1, characterized in that, The process of forming a mixed solution from rare earth element salts, β-dicarbonyl compounds, crystallization regulators, and solvents includes the following steps: A rare earth element salt solution and a β-dicarbonyl compound solution are mixed to form an intermediate solution; A solution of the crystallization regulator is gradually added to the intermediate solution.

5. The method for preparing the ultra-high purity rare earth chelate as described in claim 4, characterized in that, The crystallization regulator solution is added at a rate of 50 mL / min to 100 mL / min.

6. The method for preparing the ultra-high purity rare earth chelate as described in claim 5, characterized in that, The concentration of the rare earth element salt solution is 0.1 mol / L-0.4 mol / L, the concentration of the β-dicarbonyl compound solution is 0.4 mol / L-1.2 mol / L, and the volume ratio of the rare earth element salt solution to the β-dicarbonyl compound solution is 1:1-1:

2.

7. The method for preparing the ultra-high purity rare earth chelate as described in claim 1, characterized in that, The operating temperature of the sublimation zone is 190 ℃-210 ℃.

8. The method for preparing the ultra-high purity rare earth chelate as described in claim 7, characterized in that, The sublimation zone undergoes a multi-stage heating and holding process, including the following steps: first, heating to 130 ℃-150 ℃ and holding for 1 h-3 h, then heating to a second temperature of 190 ℃-210 ℃ and holding for 2 h-4 h; The condensation deposition zone undergoes a multi-stage heating and holding process, including the following steps: first, heating to 130 ℃-150 ℃ and holding for 1 h-3 h, then heating to 150 ℃-170 ℃ and holding for 2 h-4 h.

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